The objective of this study will be to assess the effect, if any, of losartan on the pharmacokinetics of phenytoin and phenytoin on the pharmacokinetics of losartan. Alteration in the pharmacokinetics of losartan or phenytoin may lead to clinical effects/adverse effects requiring a dose adjustment. A secondary objective will be to establish the duration of induction once phenytoin is discontinued, by using the ration of 68-hydroxycortisol and cortisol in the urine as a marker of cytochrome P450 3A induction.